It is not the physical task of removing tars and nicotine materials from cigarette smoke that makes filter design difficult. The problem of the filter designer is to create a filter that smokers will use. In addition to the mechanics of filtering, the designer must concern himself with the smoker's motive in purchasing filtering devices, and he must consider such factors as taste, draw, appearance, custom and fashion and, of course, cost.
The filters that are incorporated as part of the cigarette by cigarette manufacturers are not designed to discourage smoking. They are designed, instead, to permit sales promotion advantages that tar and nicotine content of the smoke is low, and to make this possible at minimun cost without any discernable effect to the smoker. As a class, cigarette filters generally employ a labyrinth formed of porous material which entraps solids and semi-solids that are entrained in the smoke. They do little to condense out the more volatile tars, and most do nothing to reduce the passage of carbon monoxide.
At the other end of the scale are the filtering systems of smokers' "withdrawal kits." The more effective forms of these kit devices combine condensation of tars, nicotine and other compounds by ambient cooling air with a very efficient mechanical filter. The kits usually include several filtering units, each of which is effective in removing a different percentage of the harmful materials from cigarette smoke. Cost considerations usually dictate that the same mechanical filter be used in each individual unit of the kit and that effectiveness be controlled as a function only of the volume amount of ambient air that is added to the smoke.
For the smoker who is determined to quit smoking, the well designed withdrawal kit provides an effective means for accomplishing the goal. However, most kit users have, or adopt, as their goal the reduction in the amount of tar elimination of more tar and nicotine than is removed from conventional filtered cigarettes, and to accomplish this without giving up smoking.
While such a smoker demands the "kick" that is provided by the nicotine, the quantity required to provide that kick is determined primarily by the quantity of nicotine that he is accustomed to inhaling. The withdrawal kit user is given a set of holders each which removes progressively more nicotine. After a brief time, following change to the next more effective filter, his body becomes adjusted to a lower nicotine level. The result is that he still experiences a "kick" notwithstanding that his nicotine and tar intake has been reduced. Thus, it is not lack of "kick" that is responsible for the fact that many withdrawal kit users abandon them. Industry experience is that resistance to use of effective filtering may more likely arise because of the amount of inhalation suction, or the change of flow resistance, or draw, during inhalation, does not feel right. In addition, there is resistance to the frequent cleaning that is required in most withdrawal kits. Further, there is also a reluctance in some cultures and some socio-economic groups to be seen using the cigarette holder that is employed in withdrawal kits.
A majority of withdrawal kit users eventually abandon their use because of draw or feel, prejudice against using holders, cost, or the inconvenience of cleaning. Thus, despite the availability of very effective filtering without loss of "kick" or taste, more improvement has been required in the campaign to reduce the harmful effects of smoking.